Full sequence metal and barrier layer electrochemical mechanical processing

ABSTRACT

A method and apparatus for electrochemically processing metal and barrier materials is provided. In one embodiment, a method for electrochemically processing a substrate includes the steps of establishing an electrically-conductive path through an electrolyte between an exposed layer of barrier material on the substrate and an electrode, pressing the substrate against a processing pad assembly, providing motion between the substrate and pad assembly in contact therewith and electrochemically removing a portion of the exposed layer during a first electrochemical processing step in a barrier processing station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/941,060, filed Sep. 14, 2004 now U.S. Pat. No. 7,084,064, which isincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a method forelectrochemical processing.

2. Description of the Related Art

Electrochemical mechanical planarizing (ECMP) is a technique used toremove conductive materials from a substrate surface by electrochemicaldissolution while concurrently polishing the substrate with reducedmechanical abrasion compared to conventional planarization processes.ECMP systems may generally be adapted for deposition of conductivematerial on the substrate by reversing the polarity of the bias.Electrochemical dissolution is performed by applying a bias between acathode and a substrate surface to remove conductive materials from thesubstrate surface into a surrounding electrolyte. Typically, the bias isapplied to the substrate surface by a conductive polishing material onwhich the substrate is processed. A mechanical component of thepolishing process is performed by providing relative motion between thesubstrate and the conductive polishing material that enhances theremoval of the conductive material from the substrate.

In many conventional systems, ECMP of the conductive film is followed bya conventional chemical mechanical processing for barrier removal. Thisdichotomy of processing (e.g., ECMP and CMP on a single system) requiresdivergent utilities and process consumables, resulting in higher cost ofownership. Moreover, as most ECMP processes utilize lower contactpressure between the substrate being processed and a processing surface,the heads utilized to retain the substrate during processing do notprovide robust processing performance when utilized for convention CMPprocesses, which typically have high contact pressures, which results inhigh erosion of conductive material disposed in trenches or otherfeatures. As the removal rate of low pressure conventional CMP barrierlayer processing is generally less than about 100 Å/min, conventionalCMP processing of barrier materials using low pressure is not suitablefor large scale commercialization. Thus, it would be advantageous for asystem to be enabled to remove barrier materials, such as ruthenium,tantalum, tantalum nitride, titanium, titanium nitride and the like,through an electrochemical process.

Thus, there is a need for an improved method and apparatus forelectrochemical processing of metal and barrier materials.

SUMMARY OF THE INVENTION

Embodiments of the invention generally provide a method for processingbarrier and metals disposed on a substrate in an electrochemicalmechanical planarizing system. A method and apparatus forelectrochemically processing metal and barrier materials is provided. Inone embodiment, a method for electrochemically processing a substrateincludes the steps of establishing an electrically-conductive paththrough an electrolyte between an exposed layer of barrier material onthe substrate and an electrode, pressing the substrate against aprocessing pad assembly, providing motion between the substrate and padassembly in contact therewith and electrochemically removing a portionof the exposed layer during a first electrochemical processing step in abarrier processing station.

In another embodiment, a method for electrochemically processing asubstrate includes removing a conductively layer having a barrier layerdisposed thereunder at a first processing station of a system andelectrochemically removing the barrier layer at a second processingstation of the system using a low substrate to processing pad contactpressure. The system may include a processing station disposed betweenthe first and second processing stations for residual removal of theconductive layer using a multi-step removal process.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited embodiments of theinvention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

FIG. 1 is a plan view of an electrochemical mechanical planarizingsystem;

FIG. 2 is a sectional view of one embodiment of a first electrochemicalmechanical planarizing (ECMP) station of the system of FIG. 1;

FIG. 3A is a partial sectional view of the bulk ECMP station through twocontact assemblies;

FIGS. 3B-C are sectional views of alternative embodiments of contactassemblies;

FIG. 3D-E are sectional views of plugs;

FIG. 4 are side, exploded and sectional views of one embodiment of acontact assembly;

FIG. 5 is one embodiment of a contact element;

FIG. 6 is a perspective view of another embodiment of another ECMPstation;

FIG. 7 is a flow diagram of one embodiment of a method forelectroprocessing conductive and barrier materials; and

FIG. 8 depicts a graph illustrating current and voltage traces versetime for one embodiment of an exemplary electroprocessing method.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

Embodiments for a system and method for removal of conductive andbarrier materials from a substrate are provided. Although theembodiments disclosed below focus primarily on removing material from,e.g., planarizing, a substrate, it is contemplated that the teachingsdisclosed herein may be used to electroplate a substrate by reversingthe polarity of an electrical bias applied between the substrate and anelectrode of the system.

Apparatus

FIG. 1 is a plan view of one embodiment of a planarization system 100having an apparatus for electrochemically processing a substrate. Theexemplary system 100 generally comprises a factory interface 102, aloading robot 104, and a planarizing module 106. The loading robot 104is disposed proximate the factory interface 102 and the planarizingmodule 106 to facilitate the transfer of substrates 122 therebetween.

A controller 108 is provided to facilitate control and integration ofthe modules of the system 100. The controller 108 comprises a centralprocessing unit (CPU) 110, a memory 112, and support circuits 114. Thecontroller 108 is coupled to the various components of the system 100 tofacilitate control of, for example, the planarizing, cleaning, andtransfer processes.

The factory interface 102 generally includes a cleaning module 116 andone or more wafer cassettes 118. An interface robot 120 is employed totransfer substrates 122 between the wafer cassettes 118, the cleaningmodule 116 and an input module 124. The input module 124 is positionedto facilitate transfer of substrates 122 between the planarizing module106 and the factory interface 102 by grippers, for example vacuumgrippers or mechanical clamps.

The planarizing module 106 includes at least a first electrochemicalmechanical planarizing (ECMP) station 128, disposed in anenvironmentally controlled enclosure 188. Examples of planarizingmodules 106 that can be adapted to benefit from the invention includeMIRRA®, MIRRA MESA™, REFLEXION®, REFLEXION® LK, and REFLEXION LK Ecmp™Chemical Mechanical Planarizing Systems, all available from AppliedMaterials, Inc. of Santa Clara, Calif. Other planarizing modules,including those that use processing pads, planarizing webs, or acombination thereof, and those that move a substrate relative to aplanarizing surface in a rotational, linear or other planar motion mayalso be adapted to benefit from the invention.

In the embodiment depicted in FIG. 1, the planarizing module 106includes the first ECMP station 128, a second ECMP station 130 and athird ECMP station 132. Bulk removal of conductive material disposed onthe substrate 122 may be performed through an electrochemicaldissolution process at the first ECMP station 128. After the bulkmaterial removal at the first ECMP station 128, the remaining conductivematerial is removed from the substrate at the second ECMP station 130through a multi-step electrochemical mechanical process, wherein part ofthe multi-step process is configured to remove residual conductivematerial. It is contemplated that more than one ECMP station may beutilized to perform the multi-step removal process after the bulkremoval process performed at a different station. Alternatively, each ofthe first and second ECMP stations 128, 130 may be utilized to performboth the bulk and multi-step conductive material removal on a singlestation. It is also contemplated that all ECMP stations (for example 3stations of the module 106 depicted in FIG. 1) may be configured toprocess the conductive layer with a two step removal process.

The exemplary planarizing module 106 also includes a transfer station136 and a carousel 134 that are disposed on an upper or first side 138of a machine base 140. In one embodiment, the transfer station 136includes an input buffer station 142, an output buffer station 144, atransfer robot 146, and a load cup assembly 148. The input bufferstation 142 receives substrates from the factory interface 102 by meansof the loading robot 104. The loading robot 104 is also utilized toreturn polished substrates from the output buffer station 144 to thefactory interface 102. The transfer robot 146 is utilized to movesubstrates between the buffer stations 142, 144 and the load cupassembly 148.

In one embodiment, the transfer robot 146 includes two gripperassemblies, each having pneumatic gripper fingers that hold thesubstrate by the substrate's edge. The transfer robot 146 maysimultaneously transfer a substrate to be processed from the inputbuffer station 142 to the load cup assembly 148 while transferring aprocessed substrate from the load cup assembly 148 to the output bufferstation 144. An example of a transfer station that may be used toadvantage is described in U.S. Pat. No. 6,156,124, issued Dec. 5, 2000to Tobin, which is herein incorporated by reference in its entirety.

The carousel 134 is centrally disposed on the base 140. The carousel 134typically includes a plurality of arms 150, each supporting aplanarizing head assembly 152. Two of the arms 150 depicted in FIG. 1are shown in phantom such that the transfer station 136 and aplanarizing surface 126 of the first ECMP station 128 may be seen. Thecarousel 134 is indexable such that the planarizing head assemblies 152may be moved between the planarizing stations 128, 130, 132 and thetransfer station 136. One carousel that may be utilized to advantage isdescribed in U.S. Pat. No. 5,804,507, issued Sep. 8, 1998 to Perlov, etal., which is hereby incorporated by reference in its entirety.

A conditioning device 182 is disposed on the base 140 adjacent each ofthe planarizing stations 128, 130, 132. The conditioning device 182periodically conditions the planarizing material disposed in thestations 128, 130, 132 to maintain uniform planarizing results.

FIG. 2 depicts a sectional view of one of the planarizing headassemblies 152 positioned over one embodiment of the first ECMP station128. The second and third ECMP stations 130, 132 may be similarlyconfigured. The planarizing head assembly 152 generally comprises adrive system 202 coupled to a planarizing head 204. The drive system 202generally provides at least rotational motion to the planarizing head204. The planarizing head 204 additionally may be actuated toward thefirst ECMP station 128 such that the substrate 122 retained in theplanarizing head 204 may be disposed against the planarizing surface 126of the first ECMP station 128 during processing. The drive system 202 iscoupled to the controller 108 that provides a signal to the drive system202 for controlling the rotational speed and direction of theplanarizing head 204.

In one embodiment, the planarizing head may be a TITAN HEAD™ or TITANPROFILER™ wafer carrier manufactured by Applied Materials, Inc.Generally, the planarizing head 204 comprises a housing 214 andretaining ring 224 that defines a center recess in which the substrate122 is retained. The retaining ring 224 circumscribes the substrate 122disposed within the planarizing head 204 to prevent the substrate fromslipping out from under the planarizing head 204 while processing. Theretaining ring 224 can be made of plastic materials such as PPS, PEEK,and the like, or conductive materials such as stainless steel, Cu, Au,Pd, and the like, or some combination thereof. It is furthercontemplated that a conductive retaining ring 224 may be electricallybiased to control the electric field during ECMP. Conductive or biasedretaining rings tend to slow the polishing rate proximate the edge ofthe substrate. It is contemplated that other planarizing heads may beutilized.

The first ECMP station 128 generally includes a platen assembly 230 thatis rotationally disposed on the base 140. The platen assembly 230 issupported above the base 140 by a bearing 238 so that the platenassembly 230 may be rotated relative to the base 140. An area of thebase 140 circumscribed by the bearing 238 is open and provides a conduitfor the electrical, mechanical, pneumatic, control signals andconnections communicating with the platen assembly 230.

Conventional bearings, rotary unions and slip rings, collectivelyreferred to as rotary coupler 276, are provided such that electrical,mechanical, fluid, pneumatic, control signals and connections may becoupled between the base 140 and the rotating platen assembly 230. Theplaten assembly 230 is typically coupled to a motor 232 that providesthe rotational motion to the platen assembly 230. The motor 232 iscoupled to the controller 108 that provides a signal for controlling forthe rotational speed and direction of the platen assembly 230.

A top surface 260 of the platen assembly 230 supports a processing padassembly 222 thereon. The processing pad assembly may be retained to theplaten assembly 230 by magnetic attraction, vacuum, clamps, adhesivesand the like.

A plenum 206 is defined in the platen assembly 230 to facilitate uniformdistribution of electrolyte to the planarizing surface 126. A pluralityof passages, described in greater detail below, are formed in the platenassembly 230 to allow electrolyte, provided to the plenum 206 from anelectrolyte source 248, to flow uniformly though the platen assembly 230and into contact with the substrate 122 during processing. It iscontemplated that different electrolyte compositions may be providedduring different stages of processing or at different ECMP stations 128,130, 132.

The processing pad assembly 222 includes an electrode 292 and at least aplanarizing portion 290. The electrode 292 is typically comprised of aconductive material, such as stainless steel, copper, aluminum, gold,silver and tungsten, among others. The electrode 292 may be solid,impermeable to electrolyte, permeable to electrolyte or perforated. Atleast one contact assembly 250 extends above the processing pad assembly222 and is adapted to electrically couple the substrate being processingon the processing pad assembly 222 to the power source 242. Theelectrode 292 is also coupled to the power source 242 so that anelectrical potential may be established between the substrate andelectrode 292.

A meter 244 is provided to detect a metric indicative of theelectrochemical process. The meter 244 may be coupled or positionedbetween the power source 242 and at least one of the electrode 292 orcontact assembly 250. The meter 244 may also be integral to the powersource 242. In one embodiment, the meter 244 is configured to providethe controller 108 with a metric indicative of processing, such acharge, current and/or voltage. This metric may be utilized by thecontroller 108 to adjust the processing parameters in-situ or tofacilitate endpoint or other process stage detection.

A window 246 is provided through the pad assembly 222 and/or platenassembly 230, and is configured to allow a sensor 254, positioned belowthe pad assembly 222, to sense a metric indicative of polishingperformance. For example, the sensor 254 may be an eddy current sensoror an interferometer, among other sensors. The metric, provided by thesensor 254 to the controller 108, provides information that may beutilized for processing profile adjustment in-situ, endpoint detectionor detection of another point in the electrochemical process. In oneembodiment, the sensor 254 an interferometer capable of generating acollimated light beam, which during processing, is directed at andimpinges on a side of the substrate 122 that is being polished. Theinterference between reflected signals is indicative of the thickness ofthe conductive layer of material being processed. One sensor that may beutilized to advantage is described in U.S. Pat. No. 5,893,796, issuedApr. 13, 1999, to Birang, et al., which is hereby incorporated byreference in its entirety.

Embodiments of the processing pad assembly 222 suitable for removal ofconductive material from the substrate 122 may generally include aplanarizing surface 126 that is substantially dielectric. Otherembodiments of the processing pad assembly 222 suitable for removal ofconductive material from the substrate 122 may generally include aplanarizing surface 126 that is substantially conductive. At least onecontact assembly 250 is provided to couple the substrate to the powersource 242 so that the substrate may be biased relative to the electrode292 during processing. Apertures 210, formed through the planarizinglayer 290, allow the electrolyte to establish a conductive path betweenthe substrate 122 and electrode 292.

In one embodiment, the planarizing portion 290 of the processing padassembly 222 is a dielectric, such as polyurethane. Examples ofprocessing pad assemblies that may be adapted to benefit from theinvention are described in U.S. patent application Ser. No. 10/455,941,filed Jun. 6, 2003 by Y. Hu et al. (entitled “CONDUCTIVE PLANARIZINGARTICLE FOR ELECTROCHEMICAL MECHANICAL PLANARIZING”) and U.S. patentapplication Ser. No. 10/455,895, filed Jun. 6, 2003 by Y. Hu et al.(entitled “CONDUCTIVE PLANARIZING ARTICLE FOR ELECTROCHEMICAL MECHANICALPLANARIZING”), both of which are hereby incorporated by reference intheir entireties.

FIG. 3A is a partial sectional view of the first ECMP station 128through two contact assemblies 250, and FIGS. 4A-C are side, explodedand sectional views of one of the contact assemblies 250 shown in FIG.3A. The platen assembly 230 includes at least one contact assembly 250projecting therefrom and coupled to the power source 242 that is adaptedto bias a surface of the substrate 122 during processing. The contactassemblies 250 may be coupled to the platen assembly 230, part of theprocessing pad assembly 222, or a separate element. Although two contactassemblies 250 are shown in FIG. 3A, any number of contact assembliesmay be utilized and may be distributed in any number of configurationsrelative to the centerline of the platen assembly 230.

The contact assemblies 250 are generally electrically coupled to thepower source 242 through the platen assembly 230 and are movable toextend at least partially through respective apertures 368 formed in theprocessing pad assembly 222. The positions of the contact assemblies 250may be chosen to have a predetermined configuration across the platenassembly 230. For predefined processes, individual contact assemblies250 may be repositioned in different apertures 368, while apertures notcontaining contact assemblies may be plugged with a stopper 392 orfilled with a nozzle 394 (as shown in FIGS. 3D-E) that allows flow ofelectrolyte from the plenum 206 to the substrate. One contact assemblythat may be adapted to benefit from the invention is described in U.S.patent application Ser. No. 10/445,239, filed May 23, 2003, byButterfield, et al., and is hereby incorporated by reference in itsentirety.

Although the embodiments of the contact assembly 250 described belowwith respect to FIG. 3A depicts a rolling ball contact, the contactassembly 250 may alternatively comprise a structure or assembly having aconductive upper layer or surface suitable for electrically biasing thesubstrate 122 during processing. For example, as depicted in FIG. 3B,the contact assembly 250 may include a pad structure 350 having an upperlayer 352 made from a conductive material or a conductive composite(i.e., the conductive elements are dispersed integrally with or comprisethe material comprising the upper surface), such as a polymer matrix 354having conductive particles 356 dispersed therein or a conductive coatedfabric, among others. The pad structure 350 may include one or more ofthe apertures 210 formed therethrough for electrolyte delivery to theupper surface of the pad assembly. Other examples of suitable contactassemblies are described in U.S. Provisional Patent Application Ser. No.60/516,680, filed Nov. 3, 2003, by Hu, et al., which is herebyincorporated by reference in its entirety.

In one embodiment, each of the contact assemblies 250 includes a hollowhousing 302, an adapter 304, a ball 306, a contact element 314 and aclamp bushing 316. The ball 306 has a conductive outer surface and ismovably disposed in the housing 302. The ball 306 may be disposed in afirst position having at least a portion of the ball 306 extending abovethe planarizing surface 126 and at least a second position where theball 306 is substantially flush with the planarizing surface 126. It isalso contemplated that the ball 306 may move completely below theplanarizing surface 126. The ball 306 is generally suitable forelectrically coupling the substrate 122 to the power source 242. It iscontemplated that a plurality of balls 306 for biasing the substrate maybe disposed in a single housing 358 as depicted in FIG. 3C.

The power source 242 generally provides a positive electrical bias tothe ball 306 during processing. Between planarizing substrates, thepower source 242 may optionally apply a negative bias to the ball 306 tominimize attack on the ball 306 by process chemistries.

The housing 302 is configured to provide a conduit for the flow ofelectrolyte from the source 248 to the substrate 122 during processing.The housing 302 is fabricated from a dielectric material compatible withprocess chemistries. A seat 326 formed in the housing 302 prevents theball 306 from passing out of the first end 308 of the housing 302. Theseat 326 optionally may include one or more grooves 348 formed thereinthat allow fluid flow to exit the housing 302 between the ball 306 andseat 326. Maintaining fluid flow past the ball 306 may minimize thepropensity of process chemistries to attack the ball 306.

The contact element 314 is coupled between the clamp bushing 316 and theadapter 304. The contact element 314 is generally configured toelectrically connect the adapter 304 and ball 306 substantially orcompletely through the range of ball positions within the housing 302.In one embodiment, the contact element 314 may be configured as a springform.

In the embodiment depicted in FIGS. 3 and 4A-C and detailed in FIG. 5,the contact element 314 includes an annular base 342 having a pluralityof flexures 344 extending therefrom in a polar array. The flexure 344 isgenerally fabricated from a resilient and conductive material suitablefor use with process chemistries. In one embodiment, the flexure 344 isfabricated from gold plated beryllium copper.

Returning to FIGS. 3A and 4A-B, the clamp bushing 316 includes a flaredhead 424 having a threaded post 422 extending therefrom. The clampbushing 316 may be fabricated from either a dielectric or conductivematerial, or a combination thereof, and in one embodiment, is fabricatedfrom the same material as the housing 302. The flared head 424 maintainsthe flexures 344 at an acute angle relative to the centerline of thecontact assembly 250 so that the flexures 344 of the contact elements314 are positioned to spread around the surface of the ball 306 toprevent bending, binding and/or damage to the flexures 344 duringassembly of the contact assembly 250 and through the range of motion ofthe ball 306.

The ball 306 may be solid or hollow and is typically fabricated from aconductive material. For example, the ball 306 may be fabricated from ametal, conductive polymer or a polymeric material filled with conductivematerial, such as metals, conductive carbon or graphite, among otherconductive materials. Alternatively, the ball 306 may be formed from asolid or hollow core that is coated with a conductive material. The coremay be non-conductive and at least partially coated with a conductivecovering.

The ball 306 is generally actuated toward the planarizing surface 126 byat least one of spring, buoyant or flow forces. In the embodimentdepicted in FIG. 3, flow through the passages formed through the adapter304 and clamp bushing 316 and the platen assembly 230 from theelectrolyte source 248 urge the ball 306 into contact with the substrateduring processing.

FIG. 6 is a sectional view of one embodiment of the second ECMP station130. The first and third ECMP stations 128, 132 may be configuredsimilarly. The second ECMP station 130 generally includes a platen 602that supports a fully conductive processing pad assembly 604. The platen602 may be configured similar to the platen assembly 230 described aboveto deliver electrolyte through the processing pad assembly 604, or theplaten 602 may have a fluid delivery arm 606 disposed adjacent theretoconfigured to supply electrolyte to a planarizing surface of theprocessing pad assembly 604. The platen assembly 602 includes at leastone of a meter 244 or sensor 254 (shown in FIG. 2) to facilitateendpoint detection.

In one embodiment, the processing pad assembly 604 includes interposedpad 612 sandwiched between a conductive pad 610 and an electrode 614.The conductive pad 610 is substantially conductive across its topprocessing surface and is generally made from a conductive material or aconductive composite (i.e., the conductive elements are dispersedintegrally with or comprise the material comprising the planarizingsurface), such as a polymer matrix having conductive particles dispersedtherein or a conductive coated fabric, among others. The conductive pad610, the interposed pad 612, and the electrode 614 may be fabricatedinto a single, replaceable assembly. The processing pad assembly 604 isgenerally permeable or perforated to allow electrolyte to pass betweenthe electrode 614 and top surface 620 of the conductive pad 610. In theembodiment depicted in FIG. 6, the processing pad assembly 604 isperforated by apertures 622 to allow electrolyte to flow therethrough.In one embodiment, the conductive pad 610 is comprised of a conductivematerial disposed on a polymer matrix disposed on a conductive fiber,for example, tin particles in a polymer matrix disposed on a wovencopper coated polymer. The conductive pad 610 may also be utilized forthe contact assembly 250 in the embodiment of FIG. 3C.

A conductive foil 616 may additionally be disposed between theconductive pad 610 and the subpad 612. The foil 616 is coupled to apower source 242 and provides uniform distribution of voltage applied bythe source 242 across the conductive pad 610. In embodiments notincluding the conductive foil 616, the conductive pad 610 may be coupleddirectly, for example, via a terminal integral to the pad 610, to thepower source 242. Additionally, the pad assembly 604 may include aninterposed pad 618, which, along with the foil 616, provides mechanicalstrength to the overlying conductive pad 610. Examples of suitable padassemblies are described in the previously incorporated U.S. patentapplication Ser. Nos. 10/455,941 and 10/455,895.

Method for Electroprocessing Metal and Barrier Layers

FIG. 7 depicts one embodiment of a method 700 for electroprocessing asubstrate having an exposed conductive layer and an underlying barrierlayer that may be practiced on the system 100 described above. Theconductive layer may be tungsten, copper, a layer having both exposedtungsten and copper, and the like. The barrier layer may be ruthenium,tantalum, tantalum nitride, titanium, titanium nitride and the like. Adielectric layer, typically an oxide, generally underlies the barrierlayer. The method 700 may also be practiced on other electroprocessingsystems. The method 700 is generally stored in the memory 112 of thecontroller 108, typically as a software routine. The software routinemay also be stored and/or executed by a second CPU (not shown) that isremotely located from the hardware being controlled by the CPU 110.

Although the process of the present invention is discussed as beingimplemented as a software routine, some of the method steps that aredisclosed therein may be performed in hardware as well as by thesoftware controller. As such, the invention may be implemented insoftware as executed upon a computer system, in hardware as anapplication specific integrated circuit or other type of hardwareimplementation, or a combination of software and hardware.

FIG. 8 depicts a graph 800 illustrating current 802 and voltage 804traces over one embodiment of an exemplary removal or planarizing methodas discussed below. Amplitude is plotted on the Y-axis 806 and timeplotted on the X-axis 808.

The method 700 begins at step 702 by performing a bulk electrochemicalprocess on the conductive layer formed on the substrate 122. In oneembodiment, the conductive layer is a layer of tungsten about 6000-8000Å thick. The bulk process step 702 is at the first ECMP station 128. Thebulk process step 702 generally is terminated when the conductive layeris about 2000 to about 500 Å thick.

Next, a multi-step electrochemical clearance step 704 is performed toremove the remaining tungsten material to expose an underlying barrierlayer, which, in one embodiment, is titanium or titanium nitride. Theclearance step 704 may be performed on the first ECMP station 128, orone of the other ECMP stations 130, 132.

Following the clearance step 704, an electrochemical barrier removalstep 706 is performed. Typically, the electrochemical barrier removalstep 706 is performed on the third ECMP station 132, but mayalternatively be performed one of the other ECMP stations 128, 130.

In one embodiment, the bulk processing step 702 begins at step 712 bymoving the substrate 122 retained in the planarizing head 204 over theprocessing pad assembly 222 disposed in the first ECMP station 128.Although the pad assembly of FIGS. 2, 3A, 4A-C and 5, is utilized in oneembodiment it is contemplated that pad and contact assemblies asdescribed in FIGS. 3B-C may alternatively be utilized. At step 714, theplanarizing head 204 is lowered toward the platen assembly 222 to placethe substrate 122 in contact with the top surface of the pad assembly222. The substrate 122 is urged against the pad assembly 222 with aforce of less than about 2 pounds per square inch (psi). In oneembodiment, the force is about 0.3 psi.

At step 716, relative motion between the substrate 122 and processingpad assembly 222 is provided. In one embodiment, the planarizing head204 is rotated at about 30-60 revolutions per minute, while the padassembly 222 is rotated at about 7-35 revolutions per minute.

At step 718, electrolyte is supplied to the processing pad assembly 604to establish a conductive path therethrough between the substrate 122and the electrode 614. The electrolyte typically includes at least oneof sulfuric acid, phosphoric acid and ammonium citrate.

At step 720, the power source 242 provides a bias voltage between thetop surface of the pad assembly 222 and the electrode 292. In oneembodiment, the voltage is held at a constant magnitude less than about3.5 volts. In another embodiment where copper is the material beingprocessed, the voltage is held at a constant magnitude less than about3.0 volts. One or more of the contact elements 250 of the pad assembly222 are in contact with the substrate 122 and allows the voltage to becoupled thereto. Electrolyte filling the apertures 210 between theelectrode 292 and the substrate 122 provides a conductive path betweenthe power source 242 and substrate 122 to drive an electrochemicalmechanical planarizing process that results in the removal of thetungsten material, or other conductive film disposed on the substrate,by an anodic dissolution method at step 722. The process of step 722generally has a tungsten removal rate of about 4000 Å/min. The processof step 722 using the above stated parameters for copper processinggenerally has a copper removal rate of about 6000 Å/min.

At step 724, an endpoint of the bulk electroprocess is determined. Theendpoint may be determined using a first metric of processing providedby the meter 244. The meter 244 may provide charge, voltage or currentinformation utilized to determine the remaining thickness of theconductive material (e.g., the tungsten or copper layer) on thesubstrate. In another embodiment, optical techniques, such as aninterferometer utilizing the sensor 254, may be utilized. The remainingthickness may be directly measured or calculated by subtracting theamount of material removed from a predetermined starting film thickness.In one embodiment, the endpoint is determined by comparing the chargeremoved from the substrate to a target charge amount for a predeterminedarea of the substrate. Examples of endpoint techniques that may beutilized are described in U.S. patent application Ser. No. 10/949,160,(entitled ENDPOINT COMPENSATION IN ELECTROPROCESSING, filed by Y. Wanget al.), filed Sep. 24, 2004, U.S. patent application Ser. No.10/056,316, filed Jan. 22, 2002, and U.S. patent application Ser. No.10/456,851, filed Jun. 6, 2002, all of which are hereby incorporated byreference in their entireties.

The step 724 is configured to detect the endpoint of the process priorto the breakthrough of the tungsten layer. In one embodiment, theremaining tungsten layer at step 724 has a thickness between about 500to about 2000 Å.

The clearance processing step 704 begins at step 726 by moving thesubstrate 122 retained in the planarizing head 204 over the processingpad assembly 604 disposed in the second ECMP station 130. At step 728,the planarizing head 204 is lowered toward the platen assembly 602 toplace the substrate 122 in contact with the top surface of the padassembly 604. Although the pad assembly of FIG. 6 is utilized in oneembodiment it is contemplated that pad and contact assemblies asdescribed in FIGS. 2, 3A-C, 4A-C and 5 may alternatively be utilized.The substrate 122 is urged against the pad assembly 604 with a force inless than about 2 psi. In another embodiment, the force is less than orequal to about 0.3 psi.

At step 729, relative motion between the substrate 122 and processingpad assembly 222 is provided. In one embodiment, the planarizing head204 is rotated at about 30-60 revolutions per minute, while the padassembly 222 is rotated at about 7-35 revolutions per minute.

At step 730, electrolyte is supplied to the processing pad assembly 604to establish a conductive path therethrough between the substrate 122and the electrode 614. The electrolyte composition at step 730 isgenerally the same as the composition at step 722.

At a first clearance process step 731, a first bias voltage is providedby the power source 242 between the top surface of the pad assembly 604and the electrode 614. The bias voltage, in one embodiment, is held at aconstant magnitude in the range of about 1.5 to about 2.8 volts fortungsten processing, and in another embodiment is less 2.8 volts forcopper processing. The potential difference causes a current to passthrough the electrolyte filling the apertures 622 between the electrode614 and the substrate 122 to drive an electrochemical mechanicalplanarizing process. The process of step 731 generally has a removalrate is about 1500 Å/min for tungsten and about 2000 Å/min for copper.

At step 732, an endpoint of the electroprocess step 731 is determined.The endpoint may be determined using a first metric of processingprovided by the meter 244 or by the sensor 254. In one embodiment, theendpoint is determined by detecting a first discontinuity 810 in currentsensed by the meter 244. The discontinuity 810 appears when theunderlying layer begins to break through the conductive layer (e.g., thetungsten layer). As the underlying layer has a different resistivitythan the tungsten layer, the resistance across the processing cell(i.e., from the conductive portion of the substrate to the electrode292) changes as the area of tungsten layer relative to the exposed areaof the underlying layer changes, thereby causing a change in thecurrent.

In response to the endpoint detection at step 732, a second clearanceprocess step 734 is preformed to remove the residual tungsten layer. Thesubstrate is pressed against the pad assembly with a pressure less thanabout 2 psi, and in another embodiment, substrate is pressed against thepad assembly with a pressure less than or equal to about 0.3 psi. Atstep 734, a second voltage is provided from the power source 242. Thesecond voltage may be the same or less than the voltage applied in step730. In one embodiment, the second voltage is about 1.5 to about 2.8volts. The voltage is held at a constant magnitude and passes throughthe electrolyte filling the apertures 622 between the electrode 614 andthe substrate 122 to drive an electrochemical mechanical planarizingprocess. The process of step 734 generally has a removal rate of about500 to about 1200 Å/min for both copper and tungsten processes.

At step 736, an endpoint of the second clearance step 734 is determined.The endpoint may be determined using a second metric of processingprovided by the meter 244 or by the sensor 254. In one embodiment, theendpoint is determined by detecting a second discontinuity 812 incurrent sensed by the meter 244. The discontinuity 812 appears when theratio of area between the underlying layer is fully exposed through thetungsten layer that remains in the features formed in the substrate 122(e.g., plugs or other structure).

Optionally, a third clearance process step 738 may be performed toremove any remaining debris from the conductive layer. The thirdclearance process step 738 is typically a timed process, and isperformed at the same or reduced voltage levels relative to the secondclearance process step 734. In one embodiment, the third clearanceprocess step 738 (also referred to as an overpolish step) has a durationof about 15 to about 30 seconds.

The electrochemical barrier removal step 706 begins at step 740 bymoving the substrate 122 retained in the planarizing head 204 over theprocessing pad assembly 604 disposed in the third ECMP station 132. Atstep 741, the planarizing head 204 is lowered toward the platen assembly602 to place the substrate 122 in contact with the top surface of thepad assembly 604. Although the pad assembly of FIG. 6 is utilized in oneembodiment it is contemplated that pad and contact assemblies asdescribed in FIGS. 2, 3A-C, 4A-C and 5 may alternatively be utilized.The barrier material exposed on the substrate 122 is urged against thepad assembly 604 with a force in less than about 2 psi, and in oneembodiment, less than about 0.8 psi.

At step 742, relative motion between the substrate 122 and processingpad assembly 222 is provided. In one embodiment, the planarizing head204 is rotated at about 30-60 revolutions per minute, while the padassembly 222 is rotated at about 7-35 revolutions per minute.

At step 744, electrolyte is supplied to the processing pad assembly 604to establish a conductive path therethrough between the substrate 122and the electrode 614. The electrolyte composition utilized for barrierremoval may be different than the electrolyte utilized for tungstenremoval. In one embodiment, electrolyte composition provided at thethird ECMP station 132 includes phosphoric or sulfuric acid and acatalyst. The electrolyte may be adapted to prevent or inhibit oxideformation on the barrier layer. The catalyst is selected to activate theTi or other barrier layer to react selectively with a complexing agentso that the barrier layer may be removed and/or dissolved easily withminimal or no removal of copper or tungsten. The electrolyte compositionmay additionally include pH adjusters and clelating agents, such asamino acids, organic amines and phthalic acid or other organic carbolicacids, picolinic acid or its derivatives. The electrolyte may optionallycontain abrasives. Abrasives may be desirable to remove a portion of theunderlying oxide layer.

At a first barrier process step 746, a bias voltage is provided from thepower source 242 between the top surface of the pad assembly 604 and theelectrode 614. The voltage is held at a constant magnitude in the rangeof about 1.5 to about 3.0 volts. A conductive path is establishedthrough the electrolyte filling the apertures 622 between the electrode614 and the substrate 122 to drive an electrochemical mechanicalplanarizing process. The process of step 746 generally has a titaniumremoval rate of about 500 to about 1000 Å/min. Removal rates for otherbarrier materials are comparable.

At step 748, an endpoint of the electroprocess step 746 is determined.The endpoint may be determined using a first metric of processingprovided by the meter 244 or by the sensor 254. The current and voltagetraces of the electrochemical barrier removal step 706 are similar isform to the traces 802, 804 of FIG. 8, and as such, have been omittedfor brevity. In one embodiment, the endpoint of step 748 is determinedby detecting a first discontinuity in current sensed by the meter 244.The first discontinuity appears when the underlying layer (typically anoxide) begins to break through the barrier layer. As the underlyingoxide layer has a different resistivity than the barrier layer, thechange in resistance across the processing cell is indicative of thebreakthrough of the barrier layer.

In response to the endpoint detection at step 748, a second clearanceprocess step 750 is performed to remove the residual tungsten layer. Atstep 750, a second voltage is provided from the power source 242. Thesecond voltage may be the same or less than the voltage of the firstbarrier clearance step 746. In one embodiment, the voltage is about 1.5to about 2.5 volts. The voltage is held at a constant magnitude andcauses a current to pass through the electrolyte filling the apertures622 between the electrode 614 and the substrate 122 to drive anelectrochemical mechanical planarizing process. The process of step 750generally has a removal rate less than the first barrier removal step746 of about 300 to about 600 Å/min.

At step 752, an endpoint of the electroprocess step 750 is determined.The endpoint may be determined using a second metric of processingprovided by the meter 244 or by the sensor 254. In one embodiment, theendpoint is determined by detecting a second discontinuity in currentsensed by the meter 244. The second discontinuity appears when the ratioof area between the oxide layer is fully exposed through barrier layerthat remains in the features formed in the substrate 122.

Optionally, a third clearance process step 754 may be performed toremove any remaining debris from the barrier layer. The third clearanceprocess step 754 is typically a timed process, and is performed at thesame or reduced voltage levels relative to the second clearance processstep 750. In one embodiment, the third clearance process step 754 (alsoreferred to as an overpolish step) has a duration of about 15 to about30 seconds.

Thus, the present invention provides an improved apparatus and methodfor electrochemically planarizing a substrate. The apparatusadvantageously facilitates efficient bulk and residual metal and barriermaterials removal from a substrate using a single tool. Utilization ofelectrochemical processes for full sequence metal and barrier removaladvantageously provides low erosion and dishing of conductors whileminimizing oxide loss during processing. It is contemplated that amethod and apparatus as described by the teachings herein may beutilized to deposit materials onto a substrate by reversing the polarityof the bias applied to the electrode and the substrate.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for electroprocessing a substrate, comprising: establishingan electrically-conductive path through an electrolyte between anexposed layer of barrier material on the substrate and an electrode;pressing the substrate against a processing pad assembly; providingmotion between the substrate and pad assembly in contact therewith;detecting an endpoint of a first electrochemical processing step at orjust prior to breakthrough of the exposed layer of barrier material;electrochemically processing the exposed layer of barrier material in asecond electrochemical processing step in the barrier processingstation; detecting an endpoint of the second electrochemical processingstep; and electrochemically removing a portion of the exposed layerduring the electrochemical processing steps in a barrier processingstation, wherein the electrochemical processing steps of removing theexposed layer further comprises: detecting a first endpoint;electroprocessing the substrate at a slower rate; detecting a secondendpoint indicative of residual barrier material being cleared from thesubstrate; and overpolishing the substrate after detection of the secondendpoint.
 2. The method of claim 1, wherein the step of establishing aconductive path further comprises: flowing electrolyte from below theelectrode through the processing pad assembly into contact with thesubstrate.
 3. The method of claim 1, wherein the step of detecting thefirst endpoint further comprises: detecting a first discontinuity in acurrent passing between the substrate and the electrode.
 4. The methodof claim 3, wherein the step of detecting the second endpoint furthercomprises: detecting a second discontinuity in the current passingbetween the substrate and the electrode.
 5. A method forelectroprocessing a substrate, comprising: establishing anelectrically-conductive path through an electrolyte between an exposedlayer of barrier material on the substrate and an electrode; pressingthe substrate against a processing pad assembly; providing motionbetween the substrate and pad assembly in contact therewith; rotatingthe pad assembly at a rate less than about 50 revolutions per minute;detecting an endpoint of a first electrochemical processing step at orjust prior to breakthrough of the exposed layer of barrier material;electrochemically processing the exposed layer of barrier material in asecond electrochemical processing step in the barrier processingstation; detecting an endpoint of the second electrochemical processingstep; and electrochemically removing a portion of the exposed layerduring the electrochemical processing steps in a barrier processingstation.
 6. A method for electroprocessing a substrate, comprising:establishing an electrically-conductive path through an electrolytebetween an exposed layer of barrier material on the substrate and anelectrode, wherein the electrolyte further comprises a catalyst and atleast one of sulfuric acid, phosphoric acid, amino acid, organic amine,phthalic acid, organic carbolic acid, or picolinic acid or itsderivatives; pressing the substrate against a processing pad assembly;providing motion between the substrate and pad assembly in contacttherewith; detecting an endpoint of a first electrochemical processingstep at or just prior to breakthrough of the exposed layer of barriermaterial; electrochemically processing the exposed layer of barriermaterial in a second electrochemical processing step in the barrierprocessing station; detecting an endpoint of the second electrochemicalprocessing step; and electrochemically removing a portion of the exposedlayer during the electrochemical processing steps in a barrierprocessing station.
 7. The method of claim 1, wherein the barriermaterial is at least one of ruthenium, titanium, titanium nitride,tantalum and tantalum nitride.
 8. A method for electroprocessing asubstrate, comprising: establishing an electrically-conductive paththrough an electrolyte between an exposed layer of barrier material onthe substrate and an electrode; establishing relative motion between thesubstrate and the pad assembly while the substrate and the pad assemblyare in contact; rotating the pad assembly at a rate less than about 50revolutions per minute; electrochemically removing a portion of theexposed layer during a first electrochemical processing step in abarrier processing station disposed within an enclosure of a processingsystem; removing, within the processing system, a conductive layer, ifany, remaining over the barrier layer; detecting an endpoint of thefirst electrochemical processing step at or just prior to breakthroughof the exposed layer of barrier material; removing, within theprocessing system, a conductive layer remaining over the barrier layer;electrochemically processing the exposed layer of barrier material in asecond electrochemical processing step in the barrier processingstation; detecting an endpoint of the second electrochemical processingstep; and electrochemically removing a portion of the exposed layerduring the electrochemical processing steps in a barrier processingstation.
 9. The method of claim 8, wherein the step of removing furthercomprises: electrochemically processing the conductive layer.
 10. Themethod of claim 8 further comprising: transferring the substrate betweena first electrochemical processing station to the barrier processingstation.
 11. The method of claim 8, wherein the conductive layer istungsten.
 12. The method of claim 8, wherein the conductive layer iscopper.
 13. The method of claim 8, wherein the barrier material is atleast one of ruthenium, titanium, titanium nitride, tantalum andtantalum nitride.